Conventional flow cytometers cause a number of particles such as cells to flow in a straight line in aqueous suspension. These particles are analyzed using a hydrodynamic method, whereby light is radiated onto particles flowing through a flow channel, thereby detecting the scattered light and fluorescent light from the particles and converting it to electronic signals for analysis. An important feature of the flow cytometer makes it possible to quickly analyze many particles at one time.
In FIGS. 3 and 4, such a conventional flow cytometer is shown.
Flow cell 10 has a flow channel lOa in which particles to be analyzed flow together with a sheath liquid. Each particle flows in a straight line in the flow channel lOa due to the hydrodynamic effect caused by the flow of sheath liquid. Focusing lens 7 focuses a beam Lo from a laser (not shown) onto particles flowing through the flow channel lOa.
Right angle light signal detecting assembly 21 is disposed in the y-axis plus direction and is perpendicular to the forward direction of beam Lo. The right angle signal light detecting assembly 21 contains light path tubes 22 and 23 and light path tube 22 is inserted into light path tube 23 in order to make the focusing adjustment as easy as possible. Light path tube 22 has collecting lenses 24 and 25 while tube 23 has pinhole 26 and light detector 27. The right angle signal L2 produced by a particle is collected by lenses 24 and 25, with its background noises eliminated by pinhole 26, is then received at light detector 27 where it is converted into electronic signals.
A forward scattering light detecting assembly 31 is disposed in the forward direction of the beam Lo (x-axis plus direction). The light detecting assembly 31 has light path tubes 32 and 35, (lens and pinhole not shown) and light detector 37, which receives scattered light L1 produced by particles and converts it into electronic signals. Beam blocker 33 prevents beam Lo from entering into light detector 37.
In the above-mentioned conventional flow cytometer, the light axis of right angle signal light detecting assembly 21 is required to be adjusted on the light radiating point A of flow channel lOa. In order to adjust the light axis with respect to the z-axis direction, it is well-known that light path tube 22 is provided with adjustment mechanism 20 for slideably adjusting in the z-axis direction and moving the end portion 22a of the light path tube slide in the z-axis direction by rotating adjustment screw 20a as shown in FIG. 3.
However, there are two problems with respect to the vertical movement caused by adjustment mechanism 20 as shown in FIG. 3. First, the mechanism 20 cannot slide end portion 22a smoothly. Second, after the adjustment of end portion 22a is completed, tightening the adjustment screw 20a to fix the position of end portion 22a causes a slight displacement of the adjusted position of end portion 22a thereby requiring a very expensive adjustment mechanism to avoid such displacement.
Further, if the entire right angle signal light detecting assembly is desired to be moved, a larger adjustment mechanism is required, thereby increasing the cost of the device and the complexity in its operation as well as making the smooth movement of adjustment more difficult.